Abstract
OBJECTIVE To provide evidence for breast cancer prevention and control through epidemiological analysis of the incidence, mortality and survival rate of female breast cancer patients in Beijing.
METHODS The female registration data in the Beijing urban area from 1982 to 2001 were retrospectively reviewed. The incidence, mortality and survival rate of female breast cancer patients were analyzed using routine and life-table statistical methods.
RESULTS During the period of 1982 to 2001, there was a trend of an average annual increase of female breast cancer incidence of 4.6% in urban Beijing, and of 4.9% in the world-population standardized incidence. The epidemiological features of urban Beijing female breast cancer showed: (1)The incidence distribution of different age groups from 25 to 80 years elevated with two peaks at ages of 45 ~ and 70~ years; (2)There was an elevation in each age group over the last 20 years; (3)The incidence rate at ages of 35 to 64 reached 95.3/106, causing breast cancer to become the number one cancer in females. The changes in the survival rate showed the following: the 5-year observed survival rate (OSR) increased from 62.0% in 1982-1983 to 68.7% in 1987~1988, and the relative-survival rate (RSR) increased from 66.3% to 74.2%. The 10-year OSR and RSR in 1987~1988 were 60.3% and 65.1%, and at 15 years 57.5% and 61.3%, respectively. The mortality rate of breast cancer patients fluctuated from 8 to 10 per 105 population over the 20 years of study.
CONCLUSION There is a trend of an annual increase in female breast cancer in Beijing. The 5-year survival is being improved gradually while the mortality remains stable. The results demonstrate that the principles of "early prevention, diagnosis and treatment" for breast cancer are effective in Beijing.
keywords
About 30-years of information concerning cancer morbidity and mortality has been collected by the Cancer Registration Office of Beijing since its establishment in 1976. The information suggested that lung cancer and female breast cancer (FBC) are relatively serious hazards for residents of Beijing. Lung cancer accounted for 21.7% of all malignant neoplasms and breast cancer accounted for 21.9% of cancer cases among females. Therefore, these two kinds of cancer should receive more attention. In this report, we present the epidemiological descriptive results concerning morbidity, mortality and survival of FBC patients with the goal of providing evidence for prevention and control of FBC in Beijing.
Materials and Methods
Materials
The Beijing Cancer Registration Office provided data of FBC morbidity and death from four districts (Dongcheng, Xicheng, Xuanwu, Chongwen) from 1982 to 2001. The Statistical Bureau of Beijing provided corresponding data for the four district population.
Quality control
A follow-up has been conducted for the 2.36 million residents in the four districts to verify and complete the records. Two sample surveys were completed in 1984 and 1992 to evaluate the completeness and accuracy of the cancer reporting system and completeness was found to be 92.4%.[1, 2] Among these cancer reports, the final diagnosis for 71.4% of the cases was made on pathological or cytological evidence, 28.1% on X-ray, ultrasonic or biochemical examinations and 0.5% on clinical symptoms.[3]
Follow-up
A two-stage follow-up was completed. From 1982 to 1987, we follow-up-visited 491 FBC cases among 7,284 cancer morbidity cases diagnosed from January 1 1982 to December 30, 1983. The second-stage follow-up was conducted from 1987 to 2002 among 661 FBC cases screened from 7,897 cancer cases, who were diagnosed from June 1,1987 to December 30,1988.
Statistical methods
FBC corresponds to codes 174 in ICD-9 and C50 in ICD-10. We tabulated the incidence, standardized incidence, and truncated-age incidence rate at 35 ~64 years of age, mortality and standardized mortality by years, gender and age group. Observed-survival rate (OSR) at 5 years, relative-survival rate (RSR),[4] 10 and 15-year survival rates were analyzed by life tables.
Results
Hazard of FBC in the Beijing urban area
Morbidity of FBC and its sequence lists
From 1982 to 2001, 7,350 FBC cases were reported in the four districts of Beijing. In 1982, FBC (n=234) accounted for 14.4% of all female malignant neoplasms (n=1621). Following lung cancer, FBC was the 2nd most common neoplasm among females. However in 2001, 578 FBC cases accounted for 21.9% of all female malignant neoplasms (n=2,635) and FBC had became the most common female neoplasm.
Incidence and mortality of FBC
Table 1. shows the incidence and mortality of FBC in Beijing from 1982 to 2001. There was an increase of 91.0% over the 20 years and an annual rate of increase of 4.6%. If the annual FBC incidence was standardized by the world population to exclude an aging factor, the incidence rate increased from 18.7/105 to 37.1/105. The increasing rate in the standardized incidence was 98.4% over the 20 year period with an annual increase of 4.9%. Therefore, the elevation in the FBC incidence among females of Beijing was significant. However, the FBC mortality remained relatively stable, fluctuating from 8/105 to 10/105, showing that the patients suffering from FBC can expect an relatively optimistic life span.
Incidence and mortality of FBC patients patients in Beijing, 1982~2001(1/105)
Epidemiology of female breast cancer in Beijing
Age distribution of FBC cases
Two-noticeable peaks in the elevation of FBC incidence were found during 1982 and 1983. The incidence of FBC started to increase quickly at an age of 35 years with the first peak developing at an age of 50 years (59.4/105). Then, a little decrease was observed after 55 years of age until the second noticeable peak occurred at 65 years of age (57.3/105). Then the incidence decreased with residents older than 80 years showing an incidence of 38.7/105. The pattern of age distribution of FBC from 1991 to 1992 was similar to that of 1982 ~1983 but the incidence slightly increased in every age group. However, the nature of the age distribution in 2000~2001 was quite different. Besides an increase of incidence in every age group, the two peaks in the distribution were very obvious (Table 2). In addition, the first peak moved to an earlier age group (5 years). The peak value occurred in the age group of 45~ and reached a level of 189.6/105, i.e. 2.2 times greater than that at 1982 ~1983. The second peak occurred in a delayed age group (5 yeas) near the age of 70-years. The peak value was 108.9/105, 1.9 times ofthat of 1982-1983.
Age specified incidence of breast cancer patients in Beijing
Truncated age-adjusted rate of FBC
The truncated age-adjusted rate is often used in descriptive epidemiology to illustrate the hazards of malignant neoplasms to the health of economically productive population. It is also a indirect index of hazards to economics. From 1982 to 2001, the truncated age adjusted rate of FBC doubled (increased from 45.8/105 to 95.3/105).
Survival rate of FBC patients
When compared with other common malignant neoplasms, the survival rate of FBC cases was relatively optimistic. During 1982 ~1983 and 1987~1988, the FBC victims were found to have a 5~year relative survival rate of approximately 70% while the value for lung cancer patients was only 10%. The 5~year OSR for FBC cases was 62.0% during 1982~1983 and the RSR 66.3%. However during 1987 and 1988 the OSR increased to 68.7% and the RSR reached 74.2% (Table 3). The 10~year OSR and 10~year RSR of FBC were 60.3% and 65.1% respectively at the same time, similar to 15~year OSR and 15~year RSR (OSR=57.7% and RSR=61.3). These results suggested that the long-term prognosis of 5-year survivors was favourable.
The survival rate of patients with some common neoplasms in Beijing
Discussion
Most developed countries, which have a high FBC incidence, have maintained a stable incidence since the 1990’s,[5] while some developing countries, such as China, have experienced a rising incidence,[6,7] thus attracting a great deal of attention. Our research results have shown that there was an annual increase in the FBC incidence in Beijing of 4.6% from 1982 to 2001, surpassing the international average increase of 2%. Although the FBC incidence reached 40.1/105 during 2000 and 2001, the mortality of the FBC cases remained relatively stable fluctuating between 8/105 and 10/105.
The 5-year RSR is often used internationally to evaluate the hazards of neoplasms to social health. The 5-year RSR for FBC patients was 66.3% in Beijing during 1982 and 1983 followed by an increase to 74.2% during 1987 and 1988. This enhanced RSR indicated that the degree of healing rate and life span of FBC patients had been improved. The improvements have resulted from a better FBC census, early diagnosis and treatment,[8] and introduction of new medical technology.
The alternation of the two peaks in the age distribution of FBC cases suggested that the risk or exposure to factors resulting in FBC had changed. Socioeconomic development, alternation in life style, changes in eating habits and augmentation of metal stress[9, 10] may have been influential. The results of this research may be useful for further FBC epidemiological studies to seek prevention and cures for FBC.
The truncated age-adjusted rate of FBC had greatly increased over the 20 year period of our study, reaching 95.3/105 in 2001, and becoming the most common cancer among females. This disease strongly impairs working females between 35 and 64 of age, but also is a detriment on society, economics, family and mental health. Therefore, it is imperative that the risk factors be identified through research so that this increase in FBC may be prevented in the future.
- Received September 14, 2006.
- Accepted December 10, 2006.
- Copyright © 2006 by Tianjin Medical University Cancer Institute & Hospital and Springer
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